1. Field of the Invention
This invention relates to a semiconductor device, and more particularly to a semiconductor device in which a stress is applied to the channel section to distort the crystal, thereby increasing the carrier mobility.
2. Background Art
In recent years, as the performance required for semiconductor transistors becomes higher, the structure thereof has been reconsidered. In the meantime, a multigate transistor having a three-dimensional structure called “FinFET” is proposed (see, e.g. JP 2005-159362A).
In a planar transistor, a source, a channel, and a drain are arranged in a planar configuration, and a gate electrode is provided above the channel via a gate insulating film.
In contrast, in a “FinFET” structure, the semiconductor layer including the source, the channel, and the drain is shaped like a fin (beam), and a gate electrode encloses the channel on its both sides via an insulating film.
The “FinFET” has a larger gate area than the planar transistor of the same size, and hence has a large driving current, which leads to devices having higher speed. To further increase the driving current, it is effective to apply stress to the channel to distort the crystal, thereby increasing the carrier mobility. In this case, it is important how to effectively apply stress to the channel.